Adaptation Of Layers And Well Patterns Of CO₂ Drive In Ultra-Low Permeability Beach-Bar Sand Reservoir

Aiming at the problems of low plane sweep coefficient and unbalanced vertical displacement in the development of beach-bar sand reservoirs with CO₂ injection,based on the analysis of the CO₂ flooding laws of beach-bar sand reservoirs,considering the start-up pressure gradient and reservoir fracturing reforms.The goal is to improve the horizontal and vertical balanced displacement of the reservoirs,the well pattern matching method of CO₂ flooding in low-abundance and ultra-low permeability beach-bar sand reservoirs is studied,which provides theoretical and technical support for the development of CO₂ flooding in beach-bar sand reservoirs.On the basis of studying the influencing factors and injection-production capacity of CO₂flooding in beach-bar sand reservoirs,considering start-up pressure gradient and reservoir fracturing,numerical simulation technology and calculation analysis method are applied to study the reasonable well spacing of CO₂ flooding in beach-bar sand reservoirs.Further carry out research on the adaptation and optimization of CO₂ flooding well pattern and reservoir development characteristics and reservoir reconstruction technology,as well as the optimization and adjustment of well positions.Vertically,the research on the optimization of CO₂ flooding formation combination in multi-thin beach-bar sand reservoirs is carried out,the influencing factors of formation combination are analyzed,the comprehensive characterization indexes are established,and the boundary value is determined,and the optimization method of formation combination is established.The research results are applied to the target reservoir.The research results are as follows.（1）The greater the miscibility degree,permeability and injection production pressure difference,the better the CO₂ flooding effect.Fracturing can improve the oil recovery rate.The relationships between gas breakthrough time,average daily gas injection before gas breakthrough,peak daily oil production and permeability,injection production pressure difference and crude oil viscosity are fitted.（2）The technical limit well spacing increases with the increase of injection production pressure difference and permeability.Fracturing can increase the technical limit well spacing.The economic limit well spacing and the economic optimal well spacing decrease with the increase of crude oil price,and increase with the increase of crude oil cost.（3）The five-point well pattern has a better effect on the seven kinds of beach-bar sand reservoir models.The oil displacement effect is best when the angle between fracture direction and injection-production direction is 45°.The suitable fracture length in different reservoirs models is analyzed.The well location of heterogeneous reservoir is optimized and adjusted.（4）By using the orthogonal test method,the influence degree of the influencing factors of the strata combination is determined as follows:oil saturation,reservoir permeability,crude oil viscosity and reservoir thickness.The influence of fracturing on the reservoir is transformed into the change of the average permeability of the reservoir,and the calculation chart of the average effective permeability of the reservoir under different fracturing levels and fracturing scales is established.The comprehensive effective mobility is established as the comprehensive characterization index of the formation combination,and the calculation chart of increasing multiple of average effective permeability is established.（5）The research results have achieved good development results in the target oil reservoirs.